Clinical decision support systems (CDS) are seen as a significant benefit to electronic medical records (EMRs). The use of CDS systems has been shown to improve adherence to medical evidence and increase the rate of adoption of new evidence. Many open source EMRs from small vendors do not provide CDS, because of the complexity of building them. Moreover, existing CDS functions often use proprietary knowledge representation, impeding knowledge exchange and update. This paper reports on our work on encapsulating standardized CDS functionality in a re-usable component that is agnostic of any particular EMR product. The component has been integrated with a sample EMR system and evaluated with a set of preventive care guidelines.